JPH04106519A - Liquid crystal mirror for vehicle - Google Patents

Abstract

PURPOSE:To eliminate the movement of spacers which is caused by vibration, to improve the durability, and to enable the sufficient vibration of an outside substrate and the sufficient removal of liquid drops by fixing the spacers for holding a liquid crystal charged gap to either of inside and outside substrates. CONSTITUTION:For the liquid drop removal, a specific AC current is supplied to a piezoelectric element 20 and a diaphragm 16 is vibrated with an ultrasonic wave at a specific frequency. This vibration is transmitted to the inside glass substrate 10 through an adhesive 18 for diaphragm fixation and also sent to the outside glass substrate 36 through a sealing agent 32 for a liquid crystal cell. The spherical spacers 38 are adhered only to an oriented film 34, i.e. the substrate 10, so the substrates 10 and 26 can be vibrated almost independently of each other. The vibration caused by the piezoelectric element 20 is transmitted to the outside glass substrate 26, which is vibrated sufficiently to efficiently remove liquid drops sticking on the surface of the substrate 26. Further, the crystal state of liquid crystal 30 is varied by turning on and off the application of a voltage between transparent electrodes 24 and 28 to switch the nonglaring state of the mirror.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal mirror for a vehicle, particularly one having an anti-glare function and a droplet removal function.

[Prior Art] Conventionally, in vehicles, outside mirrors such as door mirrors and fender mirrors have been used in addition to room mirrors installed in the vehicle interior in order to widen the driver's vision.

Such an outer mirror has a problem in that during rainy weather, raindrops (liquid droplets) adhere to the mirror surface, making it difficult to see. Therefore, a device is known in which a vibrating device is attached to the mirror and the mirror is vibrated appropriately to shake off the attached droplets (for example, Utility Model Application No. 63-25658
Publication No.).

On the other hand, there are anti-glare mirrors used for the rear visibility of vehicles that change the reflectance of the mirror and switch between anti-glare and non-dimming modes in order to reduce the glare from the headlights of vehicles traveling behind at night. . And, as this anti-glare mirror,
It is common to use a movable prism and change the reflectance by moving the prism to switch between anti-glare and non-dazzle. However, in such an anti-glare mirror, the driver must manually switch between anti-glare and non-dimming. For this reason, anti-glare mirrors have only been used in room mirrors located close to the driver.

However, some anti-glare mirrors include liquid crystal mirrors that can be electrically switched between anti-glare and non-glare, and by using this liquid crystal mirror, it is possible to use an anti-glare mirror as the outer mirror as well. Therefore, there are some proposals regarding this (for example, Japanese Utility Model Application Publication No. 59-68302).

Here, a liquid crystal mirror is a liquid crystal cell in which a liquid crystal is sandwiched between transparent electrodes on the surface of a reflecting mirror, and the light transmittance of the liquid crystal cell is changed by applying or not applying a voltage to the transparent electrodes. This is to switch between glare and non-dazzle.

[Problems to be Solved by the Invention] As described above, it is known to attach a vibration device for removing droplets to an outer mirror and to use a liquid crystal mirror. Therefore, the present inventors provided a vibrating device for removing droplets on the liquid crystal mirror, considered adopting this device for the outer mirror, and conducted various experiments to vibrate the liquid crystal mirror.

However, when a vibration device is added to the liquid crystal mirror,
It was found that there were problems with durability and that the mirror surface did not vibrate enough to remove droplets.

Therefore, we conducted more detailed experiments and analyzes on this point, and obtained the following findings.

That is, a liquid crystal cell holds liquid crystal between electrodes by a pair of glass substrates that support transparent electrodes. However, if the distance between the transparent electrodes is not constant, the current density (ie, reflectance) will be non-uniform, making it impossible to obtain sufficient performance. Therefore, in the liquid crystal cell, a large number of spacers are scattered between both transparent electrodes, thereby maintaining the distance between them.

In normal cases, this spacer is often fixed by pressing the glass substrates on both sides. However, when the liquid crystal mirror is vibrated as described above, it is thought that the spacer will move due to this vibration, and the liquid crystal cell will no longer be able to function and sufficient durability will not be obtained.

On the other hand, if the spacer is bonded to both glass substrates, movement of the spacer can be suppressed and durability can be improved.

However, when a spacer is bonded to both glass substrates, the vibration at this point is restricted, so both glass substrates vibrate as if they were a single thick piece of glass. It is thought that it will not be possible to vibrate sufficiently.

In particular, the vibration source for vehicle mirrors is desired to be small, lightweight, and low power, so there is a demand for a small vibration source, and a structure that can efficiently vibrate the mirror surface is desirable. It will be done.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a liquid crystal mirror that can effectively remove droplets using a small vibration source and has sufficient durability.

That is, based on the above findings, the present inventors considered bonding the spacer to only one glass substrate in order to achieve sufficiently efficient vibration while maintaining sufficient durability.

In addition, regarding the use of a spacer in a simple liquid crystal cell, the fixing of the spacer to both or one of the glass substrates, etc., are described in JP-A-58-142316, JP-A-61-2129, and JP-A-61. This is shown in, for example, Japanese Patent No.-67830.

[Means for Solving the Problems] A liquid crystal mirror for a vehicle according to the present invention includes a reflecting mirror, a vibration source provided on the back side of the reflecting mirror, an inner substrate arranged on the front side of the reflecting mirror, an outer substrate disposed on the inner substrate at predetermined intervals; a liquid crystal layer formed between the inner substrate and the outer substrate; and a liquid crystal layer fixed to either the inner substrate or the outer substrate within the liquid crystal layer. A spacer is arranged to maintain a distance between the inner substrate and the outer substrate.

[Function] The liquid crystal mirror according to the present invention has the above-described configuration, and vibrations from the vibration source are transmitted to the inner substrate and the outer substrate, and these are vibrated.

Here, since the spacer is adhesively fixed to the inner substrate or the outer substrate, the spacer does not move due to vibration, and durability can be improved.

Since the spacer is fixed to only one substrate, there is no vibration suppressing effect due to adhesion of both substrates, and the outer substrate can be sufficiently vibrated to achieve sufficient droplet removal.

[Example 2] Hereinafter, a liquid crystal mirror according to the present invention will be explained based on the drawings.

First Embodiment FIG. 1 is a sectional view showing the structure of the first embodiment. An AJ film 12 forming a mirror surface is formed on the back surface of a glass substrate 10. is the protective film 14
covered by.

Further, on the protective film 14 on the back side of the glass substrate 10, a diaphragm 16 made of tempered glass with a thickness of 1.1 mm is fixed with an epoxy adhesive spacer 18 connecting the peripheral edges. A piezoelectric element 20 serving as a vibration source is fixed to the back surface of the diaphragm 16 with an epoxy adhesive 22.

On the other hand, a transparent electrode 24 made of ITO and having a thickness of 400 mm is arranged on the surface of the glass substrate 10.
A transparent electrode 28 made of the same ITO and having a thickness of 400 mm is disposed on the back surface of the outer glass substrate 26 at a position facing 4. The gap between both transparent electrodes 24 and 28 is filled with liquid crystal 30. In addition, in order to maintain a gap for the liquid crystal 30 and prevent the liquid crystal 30 from flowing out, a liquid crystal cell sealing material 3 is used between the transparent electrodes 24 and 28.
It is glued by 2. Furthermore, both transparent electrodes 24.2
Alignment films 34 and 36 made of polyimide and having a thickness of 1000 are provided on the surface of the substrate 8.

Further, in order to maintain a gap for the liquid crystal 30, spherical spacers 38 made of polystyrene plastic and having a diameter of 8 μm are arranged at a predetermined interval between the transparent electrodes 24 and 28. In this example, the spherical spacer 38 is bonded only to the lower alignment film 34 by an adhesive sphere 40 made of epoxy plastic and having a diameter of 4 μm.

Note that this spherical spacer 38 is first bonded to the alignment film 34.
This may be done by scattering the adhesive spheres 40 on top, then scattering the spherical spacers 38 and solidifying.

This embodiment has the above-described configuration, and by supplying a predetermined alternating current to the piezoelectric element 20 to remove droplets, the diaphragm 16 is ultrasonically vibrated at a predetermined frequency (
For example, 40-60kHz).

This vibration is transmitted to the inner glass substrate 10 via the diaphragm fixing adhesive 18, and is also transmitted to the outer glass substrate 36 via the liquid crystal cell sealant 32.

Here, in this embodiment, the spherical spacer 38 is bonded only to the alignment film 34, that is, the inner glass substrate 10. Therefore, the inner glass substrate 10 and the outer glass substrate 26 can vibrate almost independently.

Therefore, the vibration caused by the piezoelectric element 20 can be sufficiently transmitted to the outer glass substrate 26, and it can be sufficiently vibrated.

In particular, the resonant frequency of the outer glass substrate 26 is
By making the resonance frequency of the inner glass substrate 10 different from the vibration caused by this, it is possible to sufficiently vibrate only the outer glass 26, and to effectively utilize the vibration energy given by the piezoelectric element 20. It is possible to generate sufficient vibration with small vibration energy.

Therefore, droplets attached to the surface of the outer glass substrate 26 can be efficiently removed.

Furthermore, if only the outer glass substrate 26 is sufficiently vibrated in this way and the spherical spacer 38 is bonded to the inner glass substrate 10, an adverse effect on bonding can be suppressed,
Durability can be improved.

In order to make the resonance frequencies of the outer glass substrate 26 and the inner glass substrate 10 different, it is possible to use a hard material as the protective film 14 or to make the thicknesses of both glass substrates 26 and 10 different.

In addition, when changing the thickness, by making the thickness of the outer glass substrate 26 relatively thin, the thickness of the outer glass substrate 26 can be changed.
It can encourage the vibration of

According to this embodiment, the crystal state of the liquid crystal 30 can be changed by turning on and off the voltage applied between the transparent electrodes 2428, and the mirror can be switched between the anti-glare state and the non-anti-glare state.

Second Embodiment FIG. 2 is a sectional view showing the configuration of the second embodiment.
Unlike the embodiment, the adhesive sphere 40 is omitted. In this example, the spherical spacer 38 is fixed to the inner glass substrate 10 by the alignment film 34.

That is, a polyimide (polyamic acid) solution is applied onto the transparent electrode 24 by a printing method, and before this is dried and solidified, spherical spacers 38 are sprinkled.

Therefore, when the polyimide dries and solidifies, an alignment film 34 is formed, and the spherical spacers 38 are attached to the glass substrate 10.
can be fixed to.

Third Embodiment The third embodiment has the same structure as the second embodiment, but has a spherical spacer 38 bonded to the outer glass substrate 26 with an alignment film 36.

Evaluation Test Results 1 Droplet removal performance and durability tests were conducted for the first, second, and third examples.

Here, in Comparative Example 1, the spherical spacer 38 is not bonded to either the inner glass substrate 10 or the outer glass substrate 26, and in Comparative Example 2, instead of the spherical spacer, a diameter of 10
The inner glass substrate 10 and the outer glass substrate 26 are bonded together using a μm adhesive sphere 40.

Here, the raindrop removal performance test was carried out by spraying water on the mirror surface, then inputting DC 12V to the piezoelectric element 20 for 5 seconds through the drive circuit, causing ultrasonic vibration for 5 seconds, and removing the water droplets remaining on the mirror surface. The condition was evaluated on the following five levels.

5... No water droplets completely 4... Some water droplets remain in the corners 3... Some water droplets remain in the center 2... Large water droplets remain 1... Quite a few large water droplets remain. The durability test was performed by applying a voltage to the piezoelectric element 2o for 5 seconds, stopping the voltage application for 30 seconds, repeating 5 seconds of ultrasonic vibration and 30 seconds of rest (this is considered as one cycle), and applying a voltage to the piezoelectric element 2o for 30 seconds. The evaluation was based on the number of cycles during which movement and aggregation of the particles were visually observed. Note that the number n was set to 3.

Fig. 3 shows the raindrop removal performance and operational durability obtained through this test.

From this, it is understood that this example provides sufficient durability while maintaining sufficient raindrop removal performance.

Further, the second embodiment has better operational durability than the third embodiment. This is considered to be because the outer glass substrate 26 vibrates better than the inner glass substrate 1o in this example as well.

This is thought to be because the inner glass substrate 10 has an AJ protective film formed on its surface, which increases the rigidity of the inner glass substrate 10 and makes it difficult to vibrate.

Further, FIG. 4 shows test results of operational durability when the thickness of the alignment film 34 of the second embodiment was variously changed. Than this,
It is understood that the thickness of the alignment film 34 is approximately 900 layers.

On the other hand, if the thickness of the alignment film 34 becomes too thick, problems such as deterioration of the reflection characteristics of the liquid crystal mirror and difficulty in uniformly applying the alignment film 34 occur. For this reason,
The thickness of the alignment film 34 is preferably 900 to 2100, and more preferably 120 to 1800.

Furthermore, when the film thickness becomes thinner, the operational durability significantly decreases.When the spherical spacers 38 are sprayed after the alignment film 34 is applied, the viscosity of the alignment film 34 is low, so the spherical spacers 38 cause the alignment film 38 to is repelled and the spherical spacer 38
This is considered to be because the alignment film 34 in the portion markedly decreases.

[Effects of the Invention] As explained above, according to the liquid crystal mirror of the present invention, sufficient durability is maintained because the spacer for maintaining the liquid crystal filling gap is fixed to either the inner or outer substrate. At the same time, efficient vibration and droplet removal effects can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of the first embodiment of the liquid crystal mirror according to the present invention, Fig. 2 is a sectional view of the second embodiment, and Figs. 3 and 4 are test results of the embodiment and comparative example. FIG. 10... Inner glass substrate (inner substrate) 12...
- Aj2 film (reflector) 16... Vibration plate 20... Piezoelectric element (vibration source) 24.28... Transparent electrode 26... Outer glass substrate (outer substrate) 30...
・LCD

Claims (1)

[Claims] A reflecting mirror, a vibration source provided on the back side of the reflecting mirror, an inner substrate placed on the front side of the reflecting mirror, and an outer substrate placed on the inner substrate at a predetermined interval. a substrate; a liquid crystal layer formed between the inner substrate and the outer substrate; and a liquid crystal layer fixed to either the inner substrate or the outer substrate and arranged within the liquid crystal layer to maintain a distance between the inner substrate and the outer substrate. A liquid crystal mirror for a vehicle, characterized in that it has a spacer.